“After the loss of the Northern Kingdom, only the tribes of Judah (and Benjamin) in the south remained. In effect, the tribe of Benjamin was absorbed into Judah.”
Not exactly. Levi remained, as well.
2 Chronicles 11:14-17 says:
14 For the Levites left their pasture lands and their property and came to Judah and Jerusalem, for Jeroboam and his sons had excluded them from serving as priests to the Lord. 15 He set up priests of his own for the high places, for the satyrs and for the calves which he had made. 16 Those from all the tribes of Israel who set their hearts on seeking the Lord God of Israel followed them to Jerusalem, to sacrifice to the Lord God of their fathers. 17 They strengthened the kingdom of Judah and supported Rehoboam the son of Solomon for three years, for they walked in the way of David and Solomon for three years.
Here's an example of new testament evidence:
And there was a prophetess, Anna the daughter of Phanuel, of the tribe of Asher.... (Luke 2:36)
This "lost tribes" malarkey is a hoot...